From: DNA : the story of the genetic revolution by James D. Watson (2017)

The unexpectedly low human gene count provoked several op-ed page ruminations on its significance. These tended toward a common theme. Stephen Jay Gould (whose premature death tragically silenced an impassioned voice), writing in the New York Times, hailed the low count as the death knell of reductionism, the reigning doctrine of virtually all biological inquiry. This doctrine holds that complex systems are built from the bottom up. Put another way: To understand events at complex levels of organization, we must first understand them at simpler levels and piece together these simpler dynamics. And so it follows that by understanding the workings of the genome, we will ultimately understand how organisms are assembled. Gould and others took the surprisingly small human gene count as evidence that such a bottom-up approach is not only unworkable but also invalid. In light of its unexpected genetic simplicity, the human organism, argued the antireductionists, was living proof that we cannot begin to understand ourselves in relation to a sum of smaller processes. To them, our low gene number implied that nurture, not nature, must be the primary determinant of who each one of us is. It was, in short, a declaration of independence from the tyranny supposedly exercised by our genes.

Like Gould, I well appreciate that nurture plays an important part in shaping each of us. His evaluation of nature’s role, however, is utterly wrong: our low gene count by no means invalidates a reductionist approach to biological systems, nor does it justify any logical inference that we are not determined by our genes. A fertilized egg containing a chimp genome still inevitably produces a chimp, while a fertilized egg containing a human genome produces a human. No amount of exposure to classical music or violence on TV could make it otherwise. Yes, we have a long way to go in developing our understanding of just how the information in those two remarkably similar genomes is applied to the task of producing two apparently very different organisms, but the fact remains that the greatest part of what each individual organism will be is programmed ineluctably into its every cell, in the genome. In fact, I see our discovery of a low human gene count as good news for standard reductionist approaches to biology: it’s much easier to sort through the effects of 21,000 genes than 100,000.